The present invention relates to a new and improved construction of measurement apparatus which is influenced by disturbing ambient temperature fluctuations or variations and incorporating a limited volume which is filled with a medium subjected to such temperature fluctuations.
In a large number of mechanical temperature-measurement devices, the actual measurement of the temperature occurs by carrying out a pressure measurement. This pressure is produced in that a liquid, vapor, or gaseous medium enclosed within a temperature feeler, exerts a pressure upon the closed system either in accordance with its vapor pressure curve (with a liquid-vapor mixture), or however owing to its volume change (with liquids, gases and vapors). The system consists of an elastic measurement element, a transmission line and a feeler. The most frequently employed pressure measuring device is the so-called Bourdon-tube manometer or Bourdon gauge. This device is simple, inexpensive, accurate and reliable and is satisfactory for a great many applications. It is therefore obvious to use such device for temperature measurements by carrying out a pressure measurement. However, in practice it has been found that for this purpose there cannot be employed any standard Bourdon gauge. Quite to the contrary, there is employed as the measurement element a Bourdon-tube system possessing an extensively modified construction, there being provided a special construction which naturally has a decisive effect upon the price and therefore upon the market value of the device.